package demo1;

/**
 * Created with IntelliJ IDEA.
 * Description:
 * User: 28779
 * Date: 2023-04-09
 * Time: 10:05
 */
public class MySingleList {
    public class ListNode {
        public int val;
        public ListNode next;

        public ListNode(int val) {
            this.val = val;
        }
    }

    public ListNode head;

    public void createList() {
        ListNode node1 = new ListNode(12);
        ListNode node2 = new ListNode(12);
        ListNode node3 = new ListNode(12);
        ListNode node4 = new ListNode(45);
        ListNode node5 = new ListNode(56);

        node1.next = node2;
        node2.next = node3;
        node3.next = node4;
        node4.next = node5;

        this.head = node1;
    }

    public void showList() {
        ListNode cur = head;
        while(cur != null) {
            System.out.print(cur.val + " ");
            cur = cur.next;
        }
    }

    //得到单链表的长度
    public int size() {
        ListNode cur = head;
        int count = 0;
        while(cur != null) {
            count++;
            cur = cur.next;
        }
        return count;
    }

    //查找是否包含关键字key是否在单链表当中
    public boolean contains(int key) {
        ListNode cur = head;
        while(cur != null){
            if(cur.val == key) {
                return true;
            }
            cur = cur.next;
        }
        return false;
    }

    //头插法
    public void addFirst(int data){
        ListNode node = new ListNode(data);
        node.next = head;
        head = node;
    }

    //尾插法
    public void addLast(int data){
        ListNode node = new ListNode(data);
        if(head == null){
            head = node;
            return;
        }
        ListNode cur = head;
        while(cur.next != null){
            cur = cur.next;
        }
        cur.next = node;

    }

    //任意位置插入,第一个数据节点为0号下标
    public void addIndex(int index,int data) {
        ListNode node = new ListNode(data);
        int len = size();
        if(index < 0 || index > len) {
            throw new IndexOutOfBounds("任意位置插入数据的时候，index位置不合法" + index);
        }
        if(index == 0) {
            addFirst(data);
            return;
        }
        if(index == len) {
            addLast(data);
            return;
        }

        ListNode cur = head;
        for (int i = 0; i < index - 1; i++) {
            cur = cur.next;
        }
        node.next = cur.next;
        cur.next = node;
    }

    //删除第一次出现关键字为key的节点
    public void remove(int key) {
        if(head == null) {
            return;
        }
        if(head.val == key) {
            head = head.next;
            return;
        }

        ListNode prev = searchPrev(key);      //找前驱节点
        if(prev == null) {
            System.out.println("没有这个数据！！");
            return;
        }

        ListNode del = prev.next;

        prev.next = del.next;
    }
    private ListNode searchPrev(int key) {
        ListNode prev = head;
        while (prev.next != null) {
            if(prev.next.val == key) {
                return prev;
            }
            else {
                prev = prev.next;
            }
        }
        return null;
    }

    //删除所有值为key的节点
    public void removeAllKey(int key){  //利用快慢指针
        if(head == null) {
            return;
        }
        ListNode cur = head.next;
        ListNode prev = head;
        while(cur != null){
            if(cur.val == key) {
                prev.next = cur.next;
                cur = cur.next;
            }
            else {
                prev = cur;
                cur = cur.next;
            }
        }
        if(head.val == key){
            head = head.next;
        }
    }

    //清空链表
    public void clear(){
        //this.head = null;
        while (head != null){
            ListNode headNext = head.next;
            head.next = null;
            head = headNext;
        }
    }
}
